The prevention of pericarp browning and the maintenance of post-harvest quality in Vietnamese longan cv. long, using sodium metabisulfite treatment

The impact of sodium metabisulfite (Na2S2O5) treatment on the prevention of pericarp browning and the maintenance of the post-harvest quality of Vietnamese longan cv. Long during storage was studied by soaking bunches of the fruit in 2.5 or 5 or 7.5% of sodium metabisulfite solution for 5 and 10 min at room temperature and then storing them at 5 plus minus 1 degree C for 28 days. The visual appearance expressed as pericarp and flesh color; the lightness of fruit pericarp (L* value); the yellowness of fruit pericarp (b* value); polyphenol oxidase (PPO) activity; the percentage of fruit decay and fruit drop; total soluble solids (TSS) content were studied. The results show that the 10 min soaking treatment in 7.5% sodium metabisulfite solution maintained L* and b* values and low PPO activity, with the fruit showing no signs of severe pericarp browning or fruit decay throughout the 21 days in storage. Moreover, the post-harvest quality of the longan fruit revealed no difference over time; plus the percentage of fruit drop was only 5.2%, when compared with the control was 5.8% and other treatments ranged from 5.5 to 5.9%.